The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Squirrel-cage rotors for electric induction machines may include a laminated stack that defines a plurality of elongated slots. A plurality of rotor bars are provided in the elongated slots. A pair of end rings are provided at opposite ends of the laminated stack. To manufacture the squirrel-cage rotor, the laminated stack is placed in a set of molds that define cavities for forming the end rings. The cavities communicate with the elongated slots. A casting material is injected into the set of molds and fills in the cavities to form the end rings and the elongated slots to form the rotor bars.
Die-casting the rotor bars and the end rings concurrently in the same set of molds increases the complexity of the molding process. For example, shrinkage holes may be formed in the interior of the elongated slots and the end rings. The shrinkage holes affect integrity of the rotor bars and the end rings. Further, die-casting the rotor bars and the end rings in the same set of molds is more expensive and die wear generally occurs when the die-cast rotor assembly is removed from the molds.